阅读说明：本技术 可替代无机白色填料的发泡热膨胀微球及制备方法和用途 (Foaming thermal expansion microsphere capable of replacing inorganic white filler, preparation method and application ) 是由 潘仕荣 周小三 于 2020-12-25 设计创作，主要内容包括：本发明公开了一种可替代无机白色填料的发泡热膨胀微球,该发泡热膨胀微球包括树脂壳体以及包封在所述树脂壳体内的发泡剂,该发泡热膨胀微球具粒径为0.5-4微米,为高白度的微球。该可替代无机白色填料的发泡热膨胀微球的未发泡状态的直径为0.2-2微米。该发泡热膨胀微球制备方法简单,并且用于涂料、塑料、造纸、印刷油墨、化纤、橡胶、化妆品等中时具有很好的分散性,不发生沉降团聚,可代替无机白色填料。(The invention discloses a foaming thermal expansion microsphere capable of replacing inorganic white filler, which comprises a resin shell and a foaming agent encapsulated in the resin shell, wherein the foaming thermal expansion microsphere is a microsphere with high whiteness and the particle size of the foaming thermal expansion microsphere is 0.5-4 microns. The diameter of the expanded thermal expansion microspheres which can replace the inorganic white filler in an unfoamed state is 0.2 to 2 microns. The preparation method of the foaming thermal expansion microsphere is simple, has good dispersibility when being used in coatings, plastics, papermaking, printing ink, chemical fibers, rubber, cosmetics and the like, does not generate sedimentation and agglomeration, and can replace inorganic white filler.)

1. A foamed heat-expandable microsphere that can replace an inorganic white filler, characterized in that the foamed heat-expandable microsphere comprises a resin shell and a foaming agent encapsulated in the resin shell, and the foamed heat-expandable microsphere has a high-whiteness microsphere with a particle size of 0.5 to 4 μm.

2. The expanded thermally-expansive microspheres capable of replacing inorganic white fillers according to claim 1, wherein the expanded thermally-expansive microspheres capable of replacing inorganic white fillers have a diameter of 0.2 to 2 μm in an unfoamed state.

3. The foamed thermally-expansible microballs capable of replacing inorganic white fillers according to claim 1 or 2, wherein said resin shell is formed of polymerized monomers consisting of 15-35 parts by weight of acrylic monomers and 65-85 parts by weight of acrylonitrile monomers and hydrophilic functional monomers consisting of 1-10 parts by weight of ether methacrylic monomers.

4. The foamed thermally-expansible microballs capable of replacing inorganic white fillers according to claim 3, characterized in that said acrylic monomer is selected from a mixture of one or more of butyl methacrylate, butyl acrylate, cyclohexyl methacrylate, methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate and methyl acrylate.

5. The expanded thermally expandable microspheres in place of inorganic white fillers according to claim 3, wherein the ether methacrylic acid monomer is selected from the group consisting of ethyltriethylene glycol methacrylate, diethylene glycol butylether methacrylate and methoxypolyethylene glycol methacrylate.

6. Expanded thermally expandable microspheres according to claim 3, characterised in that said acrylonitrile based monomers are selected from acrylonitrile and/or methacrylonitrile.

7. Expanded thermally expandable microspheres according to claim 1 or 2, wherein the foaming agent is selected from the group consisting of isobutane, isopentane, n-pentane, isohexane, isooctane and a mixture of one or more of n-octane.

8. Expanded thermally expandable microspheres according to claim 1 or 2, characterised in that the inorganic white filler is selected from a mixture of one or more of barium sulphate, zinc oxide, calcium carbonate, aluminium oxide and talc.

9. The method for preparing expanded thermally-expansible microballs capable of replacing inorganic white fillers according to any of the preceding claims 1 to 8, characterized in that it comprises the following steps:

(1) preparation of oil phase: mixing 30-60 parts by weight of foaming agent, 15-35 parts by weight of acrylic monomer, 1-10 parts by weight of ether methacrylic monomer, 65-85 parts by weight of acrylonitrile monomer, 0.01-2 parts by weight of initiator and 0.05-0.5 part by weight of cross-linking agent at 10-20 ℃ to prepare an oil phase;

(2) preparation of an aqueous phase: dissolving 20-50 parts by weight of electrolyte in 200 parts by weight of deionized water, then adding 20-30 parts by weight of dispersion stabilizer, adding 0.1-2 parts by weight of dispersion stabilizing auxiliary agent, adding 0.1-1 part by weight of polymerization inhibitor, uniformly stirring, and then adjusting the pH value of the water phase to 3-4 by using hydrochloric acid to form a water phase;

(3) homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and homogenizing the mixed liquid by a homogenizing device at the homogenizing rotation speed of 10000-15000rpm for 15-20min to form a suspension;

(4) preparation of a thermal expansion microsphere reaction: transferring the suspension prepared in the step (3) into a high-pressure reaction kettle, reacting for 18-30 h at 40-60 ℃ and 0.4-0.8 MPa in the atmosphere of nitrogen, and drying the milky white liquid obtained after reaction after suction filtration and deionized water washing to obtain unfoamed thermal expansion microspheres;

(5) preparation of the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, carrying out high-temperature spray drying and pre-foaming, adjusting the drying temperature to be higher than or equal to the foaming temperature of the thermal expansion microspheres, and carrying out spray drying to obtain the high-whiteness foamed thermal expansion microspheres.

10. The process according to claim 9, wherein the initiator is selected from azobisisobutyronitrile and/or azobisisoheptonitrile.

11. The method according to claim 9, wherein the crosslinking agent is a trifunctional or higher crosslinking agent selected from one or more of triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanate and trimethylolpropane trimethacrylate.

12. Use of the expanded thermally-expandable microspheres according to any one of claims 1 to 8 as white fillers in coatings, plastics, paper, printing inks, chemical fibers, rubbers, cosmetics.

Technical Field

The invention relates to a thermal expansion microsphere, in particular to a foaming thermal expansion microsphere capable of replacing inorganic white filler, a preparation method and application thereof.

Background

The thermally expandable microspheres include a thermoplastic shell, which is generally composed of a thermoplastic resin such as vinylidene chloride-based copolymer, acrylonitrile-based copolymer and acrylate-based copolymer, and a foaming agent encapsulated in the shell. The blowing agent is typically an alkane. The average diameter of the existing expanded heat-expandable microspheres is generally in the range of from 10 to 50 μm, and the true density is in the range of from 1000 to 1300kg/m³When heated, the gas pressure within the shell increases and the thermoplastic shell softens, resulting in a significant increase in expanded microsphere volume, which after thermal expansion foams, has a diameter size of 20 to 500 μm and is transparent or translucent when used in a coating. When cooled, the expanded microsphere shell hardens again and the volume is fixed. The great expansion capacity of thermally expandable microspheres makes them useful as fillers in a wide variety of applications. For example, the quality of the product can be reduced, the properties of the product (such as thermal properties, acoustic properties and electrical insulation properties) can be changed and the amount of materials can be saved; the foaming thermal expansion microsphere also has the advantages of excellent solvent resistance, wear resistance, good mechanical property, no toxicity, no pollution and the like.

Titanium dioxide (titanium dioxide) is an important inorganic chemical pigment, and the main component is titanium dioxide. The production process of titanium dioxide comprises two process routes of a sulfuric acid method and a chlorination method. Titanium white powder is considered as the best white pigment in the world, and is widely applied to coatings, plastics, papermaking, printing ink, chemical fibers, rubber, cosmetics and the like. Besides titanium dioxide, barium sulfate, zinc oxide, calcium carbonate, aluminum oxide and talcum powder can also be used as white pigment fillers, however, the inorganic white pigment fillers are not easy to disperse in the use of coatings and printing ink, and are easy to agglomerate and settle, and the fillers have extremely high density, so that the weight of materials in unit volume can be greatly increased.

In addition, conventional organic particles such as acrylic resin particles can also be made into white powder with small particle size, but the particles are solid particles and have high density, and cannot effectively reduce the weight of the whole material.

Therefore, a material which can replace white fillers such as titanium dioxide and the like is needed, and the material can have good dispersibility in paint and printing ink, does not agglomerate and settle, and can reduce the density of the paint or the printing ink.

Disclosure of Invention

On one hand, the invention aims to improve the foaming thermal expansion microspheres which can replace white fillers such as titanium dioxide and the like, and the foaming thermal expansion microspheres have good dispersibility in aqueous media such as coating, plastics, papermaking, printing ink, chemical fiber, rubber and cosmetics, and do not agglomerate and settle.

In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:

a foamed heat-expandable microsphere which can replace an inorganic white filler, comprising a resin shell and a foaming agent encapsulated in the shell, wherein the foamed heat-expandable microsphere has a high-whiteness microsphere with a particle size of 0.5-4 microns after foaming expansion.

Preferably, the diameter of the above expanded heat-expandable microspheres which may replace the inorganic white filler in an unfoamed state is 0.2 to 2 μm.

Preferably, the above resin case is formed of a polymerized monomer consisting of 15 to 35 parts by weight of an acrylic monomer and 65 to 85 parts by weight of a vinylcyanide monomer, and a hydrophilic functional monomer consisting of 1 to 10 parts by weight of an ether methacrylic monomer.

Preferably, the acrylic monomer is selected from one or more of butyl methacrylate, butyl acrylate, cyclohexyl methacrylate, methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate and methyl acrylate.

More preferably, the acrylic monomer is selected from methyl methacrylate and butyl acrylate.

Preferably, the above-mentioned ether methacrylic acid monomer is selected from one or more of ethyl triethylene glycol methacrylate, diethylene glycol butyl ether methacrylate and methoxypolyethylene glycol methacrylate.

More preferably, the above-mentioned ether methacrylic monomers are selected from the group consisting of diethylene glycol butyl ether methacrylate.

Preferably, the aforementioned acrylonitrile-based monomer is selected from acrylonitrile and/or methacrylonitrile, and the like.

Preferably, the blowing agent is selected from the group consisting of isobutane, isopentane, n-pentane, isohexane, isooctane, and a mixture of one or more of n-octane.

More preferably, the blowing agent is selected from isopentane or n-pentane.

Preferably, the inorganic white filler is selected from one or more of barium sulfate, zinc oxide, calcium carbonate, aluminum oxide and talc.

The invention also provides a preparation method of the foaming thermal expansion microsphere capable of replacing the inorganic white filler, which comprises the following steps:

(1) preparation of oil phase: mixing 30-60 parts by weight of foaming agent, 15-35 parts by weight of acrylic monomer, 1-10 parts by weight of ether methacrylic monomer, 65-85 parts by weight of acrylonitrile monomer, 0.01-2 parts by weight of initiator and 0.05-0.5 part by weight of cross-linking agent at 10-20 ℃ to prepare an oil phase;

(2) preparation of an aqueous phase: dissolving 20-50 parts by weight of electrolyte in 200 parts by weight of deionized water, then adding 20-30 parts by weight of dispersion stabilizer, adding 0.1-2 parts by weight of dispersion stabilizing auxiliary agent, adding 0.1-1 part by weight of polymerization inhibitor, uniformly stirring, and then adjusting the pH value of the water phase to 3-4 by using hydrochloric acid to form a water phase;

(3) homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and homogenizing the mixed liquid by a homogenizing device at the homogenizing rotation speed of 10000-15000rpm for 15-20min to form a suspension;

(4) preparation of a thermal expansion microsphere reaction: transferring the suspension prepared in the step (3) into a high-pressure reaction kettle, reacting for 18-30 h at 40-60 ℃ and 0.4-0.8 MPa in the atmosphere of nitrogen, and drying the milky white liquid obtained after reaction after suction filtration and deionized water washing to obtain unfoamed thermal expansion microspheres;

(5) preparation of the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, carrying out high-temperature spray drying and pre-foaming, adjusting the drying temperature to be higher than or equal to the foaming temperature of the thermal expansion microspheres, and carrying out spray drying to obtain the high-whiteness foamed thermal expansion microspheres.

Preferably, the above initiator is selected from azobisisobutyronitrile and/or azobisisoheptonitrile.

More preferably, the above initiator is selected from preferably azobisisobutyronitrile.

Preferably, the electrolyte is selected from one or more of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium sulfate and potassium sulfate.

Preferably, the dispersion stabilizer is selected from silica sol.

More preferably, the silica sol is a colloidal silica solution having a concentration of 25%.

Preferably, the dispersion stabilizing aid is selected from disodium ethylenediaminetetraacetate and/or sodium lauryl sulfate.

More preferably, the dispersion stabilizing aid is selected from sodium lauryl sulfate.

Preferably, the polymerization inhibitor is selected from one or a mixture of several of sodium nitrite, methylene blue, sodium sulfide, thiourea, sodium sulfate and ammonium thiocyanate.

More preferably, the polymerization inhibitor is selected from sodium nitrite.

Preferably, the crosslinking agent is a trifunctional or higher crosslinking agent selected from one or more of triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanate and trimethylolpropane trimethacrylate.

More preferably, the above-mentioned cross-linking agent is selected from trimethyolyl isocyanates.

The invention further provides the application of the foaming thermal expansion microspheres in coatings, plastics, papermaking, printing ink, chemical fibers, rubber and cosmetics, in particular the application of the foaming thermal expansion microspheres in the coatings and the printing ink.

In another aspect, the invention provides a low-density white coating plastic, paper making, printing ink, chemical fiber, rubber and cosmetics, wherein the white filler is the foaming thermal expansion microsphere.

The invention reports the foaming thermal expansion microspheres capable of replacing white fillers such as titanium dioxide for the first time, the foaming thermal expansion microspheres are ultra-small in particle size, the diameter of the foaming thermal expansion microspheres before foaming expansion is 0.2-2 microns, the particle size of the foaming thermal expansion microspheres after foaming expansion is 0.5-4 microns, the foaming thermal expansion microspheres are high-whiteness powder microspheres, and the foaming thermal expansion microspheres can be used in coatings, plastics, papermaking, printing ink, chemical fibers, rubber, cosmetics and the like, particularly in coatings and printing ink. And because the resin shell structure of the foaming thermal expansion microsphere is similar to the main resin structure in coating, plastics, papermaking, printing ink, chemical fiber, rubber and cosmetics (especially coating or printing ink), the two are similar and compatible, and meanwhile, the shell contains hydrophilic ether functional groups, the foaming thermal expansion microsphere can be dispersed in the coating and the printing ink very easily and can be suspended without sedimentation.

The invention firstly changes the preparation method of the conventional thermal expansion microspheres, for example, the oil phase and the water phase are made into the suspension of the unfoamed thermal expansion microspheres with ultra-small particle size under the condition of high-speed homogenization (10000-15000rpm), and the foamed thermal expansion microspheres with ultra-small particle size are obtained after foaming.

Drawings

FIG. 1 is a scanning electron micrograph of the expanded thermally-expansible microballs prepared in example 1.

The expanded heat-expandable microspheres prepared in example 1 of fig. 2 were white in appearance.

Detailed Description

Aiming at the defects of inorganic white fillers such as titanium dioxide in the prior art, the inventor of the application prepares a foaming thermal expansion microsphere with an ultra-small particle size by changing the preparation process of the foaming thermal expansion microsphere for the first time, wherein the particle size of the foaming thermal expansion microsphere is 0.5-4 microns (the diameter of the foaming thermal expansion microsphere in an unfoamed state is 0.2-2 microns), and the foaming thermal expansion microsphere is a high-whiteness powder microsphere, and finds that the foaming thermal expansion microsphere can replace the inorganic white fillers such as titanium dioxide to be used in coating, plastics, papermaking, printing ink, chemical fiber, rubber and cosmetics, and the surface of a resin shell of the foaming thermal expansion microsphere has hydrophilic ether functional groups, so that the foaming thermal expansion microsphere is very easy to disperse (suspend) in the coating, the plastics, the papermaking, the printing ink, the chemical fiber, the rubber and the cosmetics, and. The present invention has been completed based on this finding.

In the description of the present invention, the acrylic monomer includes, but is not limited to, one or more of butyl methacrylate, butyl acrylate, cyclohexyl methacrylate, methyl methacrylate, ethyl methacrylate, isobornyl methacrylate, hydroxyethyl methacrylate, and methyl acrylate.

In the description of the present invention, the acrylonitrile-based monomers include, but are not limited to, acrylonitrile and methacrylonitrile.

In the description of the invention, the hydrophilic functional monomer can greatly improve the hydrophilicity of the microsphere shell and improve the dispersion performance.

In the present description, the ether methacrylic monomers include, but are not limited to, ethyltriethylene glycol methacrylate, diethylene glycol butylether methacrylate, and methoxypolyethylene glycol methacrylate.

In the present description, blowing agents include, but are not limited to, isobutane, isopentane, n-pentane, isohexane, and isooctane and n-octane.

In the description of the present invention, the inorganic white filler includes, but is not limited to, barium sulfate, zinc oxide, calcium carbonate, alumina, talc, and the like.

In the description of the present invention, the initiator includes, but is not limited to, azobisisobutyronitrile and azobisisoheptonitrile.

In the present description, the crosslinking agent is a trifunctional or higher crosslinking agent, including but not limited to triallyl cyanurate, triallyl isocyanurate, trimethallyl isocyanate, and trimethylolpropane trimethacrylate.

In the description of the present invention, the dispersion stabilizer includes, but is not limited to, silica sol.

In the context of the present invention, dispersion stabilizing aids include, but are not limited to, disodium edetate and sodium lauryl sulfate.

In the description of the present invention, polymerization inhibitors include, but are not limited to, sodium nitrite, methylene blue, sodium sulfide, thiourea, sodium sulfite, and ammonium thiocyanate.

In the description of the present invention, "plural" means two or more.

Particle size measurement of thermally expanded microspheres:

the method adopts a laser particle size distribution instrument with the model of Bettersize 2600 and a detection microscope for observation, and adopts a Shanghai rectangular optical instrument CCM-900E.

Measurement of whiteness of expanded heat-expandable microspheres:

and (5) testing by a whiteness tester, wherein the model is a good surface instrument WSB-1/2.

Examples

The following are more specific examples to develop the present invention, but the present invention is not limited to the scope of these examples. Ratios, proportions, parts, percentages herein are by weight and all temperatures are in degrees Celsius unless otherwise indicated.

Example 1

(1) Preparation of oil phase: 32g of isopentane, 7g of butyl acrylate, 10g of methyl methacrylate, 5g of diethylene glycol butyl ether methacrylate, 43g of acrylonitrile, 5g of methacrylonitrile, 0.13g of trimethylallyl isocyanate and 0.6g of azobisisobutyronitrile are mixed and stirred at 20 ℃ for 10min to 20min to form a uniform oil phase.

(2) Preparation of an aqueous phase: dissolving 40g of sodium chloride in 200g of deionized water, then adding 25g of a colloidal silicon dioxide solution with the mass concentration of 25%, adding 1g of sodium dodecyl sulfate, adding 0.25g of sodium nitrite, stirring uniformly, adding hydrochloric acid to adjust the pH value to 3, and obtaining a water phase solution.

(3) Homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and dispersing the mixed liquid in a homomixer at 12000rpm for 15min to obtain a suspension.

(4) Preparing the thermal expansion microspheres by reaction: and transferring the suspension into a high-pressure reaction kettle, reacting for 24 hours at 50 ℃ and 0.6MPa in the atmosphere of nitrogen, obtaining milky white liquid after reaction, performing suction filtration and deionized water washing, and drying to obtain unfoamed thermal expansion microspheres, wherein the average particle size of the thermal expansion microspheres is 0.8 micrometer, and the initiation expansion temperature is 116 ℃.

(5) Preparing the foaming thermal expansion microspheres: dispersing the prepared unfoamed expanded microspheres into water, and then carrying out spray drying and prefoaming, wherein the drying temperature is adjusted to 160 ℃, and the spray drying is carried out to obtain high-whiteness foamed thermal expansion microsphere powder, the average particle size is 1-2 microns, and the whiteness is 98.

Example 2

(1) Preparation of oil phase: 31g of n-octane, 5g of hydroxyethyl methacrylate, 13g of methyl methacrylate, 5g of diethylene glycol butyl ether methacrylate, 41g of acrylonitrile, 8g of methacrylonitrile, 0.15g of trimethylallyl isocyanate and 0.6g of azobisisobutyronitrile were mixed and stirred at 20 ℃ for 20 minutes to form a uniform oil phase.

(2) Preparation of an aqueous phase: 60g of potassium sulfate is dissolved in 200g of deionized water, 25g of a colloidal silicon dioxide solution with the mass concentration of 25% is added, 1.2g of sodium dodecyl sulfate is added, 0.28g of sodium nitrite is added, the mixture is stirred uniformly, hydrochloric acid is added to adjust the pH value to 2, and the formed solution is a water phase.

(3) Homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and dispersing the mixed liquid in a homomixer at 14000rpm for 16min to obtain a suspension.

(4) Preparing the thermal expansion microspheres by reaction: the suspension was transferred to an autoclave and reacted at 50 ℃ and 0.6MPa for 24h under a nitrogen atmosphere. And (3) filtering the milky white liquid obtained after the reaction, washing the milky white liquid by deionized water, and drying the milky white liquid to obtain unfoamed thermal expansion microspheres, wherein the average particle size of the thermal expansion microspheres is 0.6 micrometer, and the initiation expansion temperature is 148 ℃.

(5) Preparing the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, and then carrying out spray drying and prefoaming, wherein the drying temperature is adjusted to 200 ℃, and the spray drying is carried out to obtain high-whiteness foamed thermal expansion microsphere powder, the average particle size is 1.5 microns, and the whiteness is 98.

Example 3

(1) Preparation of oil phase: 27g of n-pentane, 15g of butyl acrylate, 2g of isobornyl methacrylate, 5.6g of ethyltriethylene glycol methacrylate, 48g of acrylonitrile, 0.25g of triallyl cyanurate and 0.6g of azobisisoheptonitrile were mixed and stirred at 20 ℃ for 10min to 20min to form a uniform oil phase.

(2) Preparation of an aqueous phase: dissolving 45g of potassium chloride in 200g of deionized water, then adding 20g of a colloidal silicon dioxide solution with the mass concentration of 25%, adding 1g of disodium ethylene diamine tetraacetate, adding 0.25g of sodium sulfite, stirring uniformly, adding hydrochloric acid to adjust the pH to 3, and obtaining a water phase solution.

(3) Homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and dispersing the mixed liquid in a homomixer at 10000rpm for 15min to obtain a suspension.

(4) Preparing the thermal expansion microspheres by reaction: the suspension was transferred to an autoclave and reacted at 50 ℃ and 0.6MPa for 24h under a nitrogen atmosphere. And (3) filtering the milky white liquid obtained after the reaction, washing the milky white liquid with deionized water, and drying the milky white liquid to obtain unfoamed thermal expansion microspheres, wherein the average particle size of the thermal expansion microspheres is 1.5 microns, and the initiation expansion temperature is 105 ℃.

(5) Preparing the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, and then carrying out spray drying and prefoaming, wherein the drying temperature is adjusted to 160 ℃, and the spray drying is carried out to obtain high-whiteness foaming thermal expansion microsphere powder, the average particle size is 3.5 microns, and the whiteness is 98.

Example 4

(1) Preparation of oil phase: 21g of isopentane, 15g of butyl acrylate, 6g of hydroxyethyl methacrylate, 6g of methoxypolyethylene glycol methacrylate, 41g of acrylonitrile, 4.5g of methacrylonitrile, 0.15g of trimethylolpropane trimethacrylate and 0.6g of azobisisoheptonitrile were mixed and stirred at 20 ℃ for 18min to form a homogeneous oil phase.

(2) Preparation of an aqueous phase: dissolving 50g of sodium sulfate in 200g of deionized water, then adding 20g of a 25% colloidal silica solution by mass, adding 1g of sodium dodecyl sulfate, adding 0.25g of thiourea, stirring uniformly, adding hydrochloric acid to adjust the pH to 2, and obtaining a water phase solution.

(3) Homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and dispersing the mixed liquid in a homomixer at 10000rpm for 15min to obtain a suspension.

(4) Preparing the thermal expansion microspheres by reaction: the suspension was transferred to an autoclave and reacted at 50 ℃ and 0.6MPa for 24h under a nitrogen atmosphere. And (3) filtering the milky white liquid obtained after the reaction, washing the milky white liquid with deionized water, and drying the milky white liquid to obtain unfoamed thermal expansion microspheres, wherein the average particle size of the thermal expansion microspheres is 1.8 microns, and the initiation expansion temperature is 103 ℃.

(5) Preparing the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, and then carrying out spray drying and prefoaming, wherein the drying temperature is adjusted to 160 ℃, and the spray drying is carried out to obtain high-whiteness foaming thermal expansion microsphere powder, the average particle size is 3.5 microns, and the whiteness is 98.

Example 5

(1) Preparation of oil phase: 26g of n-pentane, 16g of butyl methacrylate, 6g of ethyl methacrylate, 6g of diethylene glycol butyl ether methacrylate, 36g of acrylonitrile, 9.5g of methacrylonitrile, 0.15g of trimethylallyl isocyanate and 0.6g of azobisisobutyronitrile were mixed and stirred at 20 ℃ for 18min to form a homogeneous oil phase.

(2) Preparation of an aqueous phase: 42g of sodium chloride is dissolved in 200g of deionized water, 23g of a colloidal silicon dioxide solution with the mass concentration of 25% is added, 1.2g of sodium dodecyl sulfate is added, 0.15g of sodium nitrite is added, the mixture is stirred uniformly, hydrochloric acid is added to adjust the pH value to 3, and the formed solution is a water phase.

(3) Homogenizing the water phase and the oil phase: pouring the oil phase prepared in the step (1) into the water phase prepared in the step (2), and dispersing the mixed liquid in a homomixer at 15000rpm for 20min to obtain a suspension.

(4) Preparing the thermal expansion microspheres by reaction: the suspension was transferred to an autoclave and reacted at 50 ℃ and 0.6MPa for 24h under a nitrogen atmosphere. And (3) filtering the milky white liquid obtained after the reaction, washing the milky white liquid with deionized water, and drying the milky white liquid to obtain unfoamed thermal expansion microspheres, wherein the average particle size of the thermal expansion microspheres is 1.2 microns, and the initiation expansion temperature is 103 ℃.

(5) Preparing the foaming thermal expansion microspheres: dispersing the prepared unfoamed thermal expansion microspheres into water, and then carrying out spray drying and pre-foaming, wherein the drying temperature is adjusted to 165 ℃, and the high-whiteness foaming thermal expansion microspheres are obtained by spray drying, and have the average particle size of 3 microns and the whiteness of 98.

Example 6

The foaming thermal expansion microspheres prepared in examples 1 to 5, titanium dioxide and barium sulfate were added to the following coating (water-based paint for furniture), and the components and the contents of the obtained coating are shown in table 1 below.

TABLE 1 coating compositions

Remarking: the water-based acrylic resin (RICC 815, Yuan materials science and technology (Shanghai) Co., Ltd.), deionized water, a leveling dispersant digao 270, a defoamer digao 825, a film forming aid dipropylene glycol methyl ether DPM, a pH regulator AMP-95, a rheological agent DOW 8W, a rheological agent A-21D and a rheological agent DOW2020 in the table are water-based paint components for furniture.

TABLE 2 physical state of the coatings and their effect after use

Observing the physical state of the coating and the effect of the coating after use (see table 2), finding that under the conventional storage condition, the coating 1-5 using the foaming thermal expansion microspheres of the embodiments 1-5 of the invention as white fillers basically has no precipitation and agglomeration phenomenon, does not need stirring, and can be directly used; the paints 6 and 7 using titanium dioxide and barium sulfate as white fillers have serious precipitation and agglomeration phenomena, and need long-time physical stirring when in use.

After the coatings 1 to 5 are coated on furniture and dried, the whiteness of the obtained coating can reach 90 as same as that of the coating 6 and is better than the whiteness (80) of the coating 7. Moreover, the coating obtained by the coatings 1-5 has better glossiness than the coatings 6 and 7, and is more free from falling off, probably because the components of the coatings 1-5 have better dispersibility and are more uniform, the flatness of the obtained coating is better.

Moreover, the density of the coatings 1 to 5 using the foamed thermal expansion microspheres of examples 1 to 5 as white fillers was about 1.0kg/L, and the densities of the coatings 6 and 7 using titanium dioxide and barium sulfate were about 2.0kg/L, the former having a much lower density than the latter, and the transportation cost was saved.

Example 7

The foaming thermal expansion microspheres prepared in examples 1 to 5, titanium dioxide and barium sulfate were added to the following printing ink, and the components and the contents of the obtained printing ink are shown in table 3 below.

TABLE 3 ingredients and contents of printing inks

TABLE 4 physical state of the printing inks and their effect after use

Observing the physical state of the printing and the effect after the printing is used (see table 4), under the conventional storage condition, the printing ink 5 using the foaming thermal expansion microspheres of the embodiments 1 to 5 as the white filler basically has no precipitation and agglomeration phenomenon, does not need stirring, and can be directly used; the printing inks 6 and 7 using titanium dioxide and barium sulfate as white fillers have serious precipitation and agglomeration phenomena, and need long-time physical stirring when in use.

After the printing inks 1 to 5 were applied to a substrate and dried, the whiteness of the obtained pattern was as high as 90 in the printing ink 6 and better than the whiteness (85) of the coating layer of the printing ink 7. Moreover, the glossiness of the patterns obtained by printing the inks 1 to 5 is better than that of the patterns obtained by printing the inks 6 and 7, probably because the components of the printing inks 1 to 5 are better in dispersity and more uniform, and the obtained patterns are better in flatness.

The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.